The present disclosure relates generally to agricultural food animal production and more specifically to improving the performance of ventilated plenum flooring systems as an alternative to the use of bedding or litter material and/or high ventilation rates to manage manure and air quality within a commercial broiler (meat) poultry housing unit.
Commercial production of broiler poultry is generally performed in large housing units that are designed to protect poultry flocks from external threats, such as natural predators, to maintain optimal temperature/humidity conditions according to the age of the flocks, and to facilitate uniform delivery of nutrition to large flocks. In most cases, the flocks are primarily confined within the housing unit throughout their development from hatchlings to market weight mature birds. During this confinement, a bed of manure accumulates on the floor of the housing unit. Effective management of the manure bed is critical to ensuring the comfort and health of flocks.
Commercial producers have adopted specific methods for managing manure during the flock growth period. Typically, the housing unit floor is covered with a bedding or litter material to absorb and dilute manure moisture. In the United States, litter is typically reused in the same housing unit for multiple flocks in succession, resulting in a buildup of manure within the litter and a corresponding increase in ammonia production due to biochemical activity. Fresh air ventilation and other measures are used to maintain housing unit interior conditions for bird comfort and health, resulting in increased annual water and energy costs without resolving external environmental and public health concerns related to increased ammonia and other pollutant releases.
The use of a modular plenum flooring system such as the one disclosed in the Correa et al. U.S. Pat. No. 8,132,535, is an alternative to the use of litter. Such flooring systems have the potential to reduce ammonia production, reduce pathogen and insect infestation, and decrease water, fuel and electricity usage, thereby improving the health of a flock of poultry and reducing the cost of producing the flock. The shortcoming of plenum flooring systems is that they have failed to provide consistent conditions required for manure moisture control and bird comfort.
A study of the flooring system of U.S. Pat. No. 8,132,535 conducted at the University of Georgia under the sponsorship of a United States Department of Agriculture Conservation Innovation Grant concluded that the plastic flooring system, described as a Litter-less Flooring System (LFS), showed promise in reducing ammonia and airborne particulate matter, but fell short of matching or improving upon the performance of conventional litter management on factors such as bird welfare and mortality, energy usage, labor, and longevity of the system components. The study concluded that, on the basis of these results, significant further research and development would be required before the system could be considered a commercially viable product.
Following that study, tests were conducted over an 18-month period which reaffirmed the UGA study conclusions and provided insights to address each of the identified shortcomings. During the tests, thermal imaging was used to better understand variations in the flooring temperature and manure moisture, and housing unit heating was performed with both radiant and forced air heaters. The tests showed that neither heater type can maintain consistent flooring temperatures required for bird comfort during the brooding period. Radiant heaters caused localized over-heating, causing floor surface panels to buckle due to material expansion. Forced air heaters eliminated localized over-heating and eliminated lifting due to expansion but did not provide consistent floor temperatures required for bird health and comfort. Inconsistent flooring temperatures could not be alleviated by variations in the direction or rate of plenum ventilation flow.
Due to the limited mass and thermal storage capacity of plastic plenum flooring modules and rapid conductive heat losses to the ground, frequent operation of poultry housing unit heaters is required to maintain bird comfort and avoid huddling of chicks for warmth. This deficiency increases energy usage and may result in premature failure and physical damage to polymer flooring panels due to repeated overheating in attempts to improve manure drying and maintain conditions for bird comfort and welfare. Further, even with a thin moisture barrier as prescribed in the '535 patent, heat transfer between the flooring module lower panel and the ground causes buildup of condensation within the plenum space, reducing the efficiency of manure moisture removal and creating conditions for increased growth of fungi and bacteria.
The benefits of plenum flooring over litter treatments are diminished by the lack of consistent temperature and moisture control, resulting in a poultry flock that is more prone to foot pad dermatitis and may be less healthy compared to litter-based manure management methods.